The present invention relates to a vacuum heat-insulating block having its interior retained in vacuum condition so as to attain heat insulating and sound blocking features.
Conventionally, there have been developed various panels and blocks having their respective inner spaces retained in vacuum to attain enhanced heat insulating capability. A vacuum heat-insulating block has its surface covered with flexible substance and its inside depressurized to provide a vacuum pack configuration, and such a configuration leaves the block unsatisfied in strength. To overcome this disadvantage, an improved vacuum block has its surface bonded with a rigid surface material to enhance its heat insulating property and rigidity. An improved heat-insulating panel is designed in a sandwich-like multi-layered configuration with a core element having a surface element superposed at its front and rear surfaces, retaining the inside of the core element in vacuum condition to attain enhanced heat insulating property and strength.
Thus, a foamed material having high compression strength or a core member formed by assembling hexagonal or cylindrical cells, which is called a honeycomb core, is used in the vacuum panel or vacuum block so as to obtain necessary plate thickness and resist exterior pressure. The honeycomb core is characterized in that it has relatively low bulk specific gravity compared to its high compression strength.
In saying that the bulk specific gravity of the core member is low in the vacuum heat-insulating block, it means that the material constituting the inside of the core member transmits little heat and sound, and thus, it has improved heat insulating/sound blocking effects.
However, a problem arises when utilizing the honeycomb core as the core member of the vacuum block, where the side surfaces of the cells in vacuum condition collapses by the atmospheric pressure, thus incapable of maintaining the block configuration.
A panel solving this problem is disclosed in Japanese Patent Laid-Open Provisional Publications No. 10-89589 and No. 11-280199, in which the panel is formed by sandwiching the honeycomb core with surface material having rigidity, and then depressurizing the inside of the core to attain a vacuum condition.
The disclosed panel has flexural strength and rigidity, so when utilizing the panel as a structural member, the panel is preferably used to form a flat surface. However, in order to apply this structural member to a curved surface, the panel must be designed to have a desired curvature at the time of manufacture of the panel member, because it is impossible to bend the panel after completing the manufacturing process.
Therefore, it was difficult to apply the panel formed by covering a vacuum heat-insulating block with a surface member to the inner walls of vehicles or airplanes having curved outer walls.
Conventionally, when applying the vacuum heat-insulating member to a curved surface, a vacuum block having as core material a continuously foamed plastic material having flexibility and manufactured separately from the surface member is used.
Moreover, the vacuum heat-insulating block has advantageous heat insulating and sound blocking properties, but generally has poor sound absorption property. One example of the material having a sound absorption property is glass wool, but the noise absorbing effect of the glass wool is realized by the glass fibers of the glass wool being vibrated by the acoustic vibration of air and rubbed against each other, converting the vibration movement into frictional heat.
However, according to a general vacuum heat-insulating block utilizing the continuously foamed plastic material as core, the above-mentioned friction does not occur, so the block depends solely on inner acoustical loss realized by the dynamic viscosity that the core holds, and thus the noise absorbing property was limited. Even if a honeycomb core is used as the core for the vacuum heat-insulating block and glass wool is filled in the interior space of the core, since the core interior is retained in vacuum condition, the glass fibers will not be rubbed against each other, thus being unable to convert the acoustic vibration to frictional heat.
Acoustic vibration is transmitted by the vibration of the surface plate receiving sound causing the cell walls of the core to vibrate, and further causing the surface plate on the other side to vibrate. Therefore, an improved structural member is proposed having a double core structure and further having a material having viscosity adhered between the two layers, thus enabling to transmit shear force and to realize a noise absorption effect. However, according to this structure, in order for the member to attain shear force, it was impossible to realize a sufficient plate thickness enabling the member with viscosity to absorb the vibration.
Therefore, the goal of the present invention is to provide a vacuum heat-insulating block including a honeycomb core that has a noise absorption property and retains flexibility enabling the block to be bent easily.
The vacuum heat-insulating block according to the present invention basically comprises a structure including a vacuum core member enwrapped with a cover member, the vacuum core member comprising a plural number of honeycomb members being stacked, each honeycomb member formed by adhering a support plate to a honeycomb core member.
The vacuum heat-insulating block is formed by simply stacking the honeycomb members, so each honeycomb member can move freely without receiving shearing force, and thus the present block attains flexibility.
Moreover, the vacuum core member of the present vacuum heat-insulating block includes a woven or non-woven fabric having air permeability interposed between the stacked honeycomb members.
The vacuum heat-insulating block formed accordingly realizes easy and secure evacuation, thus attaining a block with a high vacuum level.
According to another example, the vacuum core member of the present vacuum heat-insulating block includes a woven or non-woven fabric having a large surface friction coefficient interposed at the superposed surfaces of the stacked honeycomb members.
The vacuum heat-insulating block formed accordingly absorbs acoustic vibration transmitted through the honeycomb members by the woven or non-woven fabric interposed between the honeycomb plates, thus realizing a sound absorbing effect.
Moreover, the vacuum core member of the present vacuum heat-insulating block includes a partition plate interposed between said stacked honeycomb members.
The vacuum heat-insulating block formed as above has improved strength reinforced by the partition plate.
Furthermore, the vacuum core member of the present vacuum heat-insulating block characterizes in that the honeycomb core member of the honeycomb member is formed of a material having dynamic viscosity.
Such vacuum heat-insulating block is capable of absorbing acoustic vibration by the dynamic viscosity of the honeycomb core member.